1. Field of the Invention
The present invention generally relates to a method and apparatus for transferring a wafer, and more particularly to a method and apparatus for transferring a wafer after removing waste washing solution from the wafer. Removal of washing solution from the wafer after the washing step prevents damage to the transferring device.
2. Description of the Related Art
During manufacture of a semiconductor device, a wafer on which integrated circuits (ICs) have been formed is subjected to a sawing step using a diamond-pointed scribing blade to divide the wafer into individual, separate, semiconductor chips. As the scribing blade rotates against the wafer, it abrades the silicon creating small silicon particles. During or after sawing, a washing solution is used to flush away the silicon particles from the wafer. In general, DI water (deionized water) is used as the washing solution.
In the manufacturing process, adhesive tape is attached to the inactive back surface of the wafer to enable manipulation of the wafer. After the wafer sawing step, the individual semiconductor chips remain adhered to the adhesive tape. During processing, a wafer supporting means, i.e., a wafer ring, is used for holding and transferring the wafer. The adhesive tape is attached to a bottom surface of the wafer supporting means which has an opening at its the center to expose the wafer and the wafer is attached to an upper surface of the adhesive tape through the opening. When the wafer is transferred, a transferring device mechanically picks up the wafer supporting means which holds and supports the wafer. The wafer is thereby protected from any damage resulting from mechanical contact between the wafer and the transferring device.
FIG. 1 is a schematic view of a conventional device for transferring a wafer and FIG. 2 is schematic view of an interior portion of the transferring device of FIG. 1. Referring to FIG. 1 and FIG. 2, adhesive tape 22 is attached to a bottom surface of a wafer supporting means 21, i.e., a wafer ring, which has an opening 24 at its center to expose a wafer 20. The wafer 20 is attached to an upper surface of the adhesive tape 22 through opening 24. Using vacuum pressure, transferring means 60 transfers wafer supporting means 21 including wafer 20, to the scribing device. The wafer 20 is subjected to a sawing step using a diamond-pointed scribing blade to divide the wafer into individual, separate, semiconductor chips 23. Silicon particles produced during the wafer sawing step are removed by spraying a washing solution such as DI water on the upper surface of the wafer 20, during or after the wafer sawing step.
After the wafer sawing and washing step, the wafer 20 is unloaded from the scribing device. The wafer supporting means 21 is then picked up using transferring means 60 by contacting the upper surface of the wafer supporting means 21 with suction cups 63 of loading arms 62 of the transferring means 60. More specifically, the transferring means 60 is composed of a loading arm body 61 and four loading arms 62, which extend from the loading arm body 61, and a gas transmitting tube 64 located within the loading arm body 61 and the loading arms 62. The four terminal ends of the gas transmitting tube 64 within the loading arms 62 are each connected to an individual suction cup 63. The terminal end of the gas transmitting tube 64 located within the loading arm body 61 is connected to vacuum generating means 67.
The vacuum pressure is exerted on the suction cups 63 using the vacuum generating means 67 which is connected to the gas transmitting tube 64, whereby wafer 20 is transferred to a designated position by moving transferring means 60.
After the wafer sawing step, however, the wafer ring retains about 40-60% of the washing solution used in the wafer washing step. This remaining washing solution is suctioned into gas transmitting tube 64 via the suction cups 63. The suctioned waste washing solution contaminates the gas transmitting tube 64 and causes failure of the solenoid which generates the vacuum, thus resulting in failure and sudden stoppage of the transferring means 60.